[S09-P] Poster

[S09-P-02] Postseismic Process of Moderate and Large Interplate Earthquakes within the Source Area of the Megathrust Earthquakes Along the Nankai Trough

Mamoru Hyodo¹, Ryoichiro Agata¹, Tsuyoshi Ichimura², ^○Takane Hori¹ (1.Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan, 2.Earthquake Research Institute, The University of Tokyo, Tokyo, Japan)

Recent two M6~7-class earthquakes occurred within the source area of great interplate earthquakes nearby the Japanese Islands were followed by contracting consequences: the 2016 Kumano-nada earthquake above wasn't followed by the great interplate earthquake, while an M7-class interplate earthquake which occurred at off-Tohoku region in March 9, 2011 was followed by the 2011 Tohoku-oki earthquake, and was regarded as one of the foreshocks of the off-Tohoku earthquake. Such different consequences are probably caused by the different preparation level of the great interplate earthquake at the timings of occurrences of these M6~7-class earthquakes. When the occurrence of great earthquake is approaching, postseismic slips after the M6~7-class earthquakes can easily propagate to the surrounding region and can trigger the subsequent great event. While, if the fault is not urgent to the great event, strong coupling on the fault may prevent postseismic slip from propagating to the surrounding area. These differences in postseismic slip patterns strongly affect the corresponding crustal deformation. Hence, from occurrence pattern of the crustal deformation after the M6-7 earthquake in the target source region, it might be possible to narrow down the subsequent scenarios that can occur. In this study, we focus on the Nankai Trough region, and firstly examine the possible propagation pattern of afterslips of the hypothetical occurrence of earthquakes such as M7-class Hyuga-nanda earthquake or M6-class Off-Kumano earthquake in many Nankai Trough earthquake scenarios deduced from numerical simulations. Then, we classify the expected postseismic deformation patterns depending on the propagation patterns of particular afterslip. In order to evaluate realistic crustal deformation, we will evaluate crustal deformation associated afterslips not only in a homogeneous elastic half-space but also in FE models with heterogeneous crustal structure and the configuration of bathymetry.